1. Field of the Invention
The present invention relates to a vehicle lamp system, and more particularly, to a vehicle lamp system having an irradiation axis regulating mechanism (or, in other terms, a leveling mechanism) and a method to improve vibration damping and shock resistance of the vehicle lamp system.
2. Description of the Related Art
There is a known mechanism for use in a vehicle lamp system which functions to automatically control an irradiation axis or cause the irradiation axis to be varied through manual operation. For example, this mechanism, such as an auto leveling instrument can regularly correct the direction of light emission from a lighting device by denying variation in the drive posture of a vehicle, which prevents the direction of light emission from the lighting device affixed to the vehicle from being unsettled due to the variation in the posture of the vehicle in its direction of travel. Other instruments are known that correct the optical axis so that the irradiation light does not vary in an undesirable direction due to a variation in the number of passengers or in the cargo-loading condition of the vehicle.
Further, a stepping motor has also been known as a driving source in an instrument of the sort mentioned above in an attempt to save electric power by stopping supply of power to the unoperated stepping motor so as to bring about the unexcited condition of each phase coil of the stepping motor.
However, one problem with such conventional instruments is that they tend to not produce a positional deviation, or an off-key condition arising from the absence of or a decrease in the holding force of a rotor during a shock condition when the stepping motor is unoperated because priority is given to power saving in the system, and therefore, vibration damping and shock resistance are not sufficiently ensured.
It is therefore an object of the present invention to sufficiently increase the vibration damping and shock resistance of an irradiation axis regulating mechanism using, for example, a stepping motor as a driving source.
In order to solve the foregoing problems, a vehicle lamp system according to the invention comprises a leveling mechanism for controlling the posture of a reflector using, for example, a stepping motor as a driving source of the leveling mechanism and is characterized in that each phase coil of the stepping motor may be excited with the same excitation phase as the last excitation phase at the time when the stepping motor was last driven or otherwise a coil in one of the last excitation phases at the time when the stepping motor was last driven before an external force, such as vibration or a shock is given to the reflector after the coils in the respective phases are totally set to a non-excited condition in the stepping motor.
It is therefore possible to prevent a rotor from being deviated from the original position or set out of tune by predicting the vibration or shock given to a reflector and causing a motor to generate necessary and sufficient holding torque.